The present disclosure relates to hydraulic control devices for automatic transmissions that are mounted on, e.g., vehicles and that include a plurality of engagement elements to be engaged and disengaged according to whether an oil pressure is supplied thereto or not.
For example, automatic transmissions using a belt-type stepless speed change mechanism that includes a pair of pulleys and a metal belt (or chain) wrapped around the pulleys and that steplessly performs shifting by changing the effective diameters of the pulleys are conventionally widely used as automatic transmissions that are preferably used for vehicles. Automatic transmissions using a toroidal-type stepless speed change mechanism, a cone ring-type stepless speed change mechanism, etc. instead of the belt-type stepless speed change mechanism are also known in the art.
Moreover, regarding these automatic transmissions, automatic transmissions have been developed which have two parallel power transmission paths, namely a first power transmission path coupling an input shaft and an output shaft via a forward-reverse switching device and a second power transmission path coupling the input shaft and the output shaft via a stepless speed change mechanism (see WO 2013/176208). In such an automatic transmission, the forward-reverse switching device has a first clutch that is engaged only when a vehicle moves forward and a brake that is engaged only when the vehicle moves backward, a synchromesh mechanism (hereinafter referred to as the synchro mechanism) is inserted in the first power transmission path, and a second clutch is inserted in the second power transmission path.
This automatic transmission therefore includes four engagement elements, namely the first and second clutches, the brake, and the synchro mechanism.